The president accompanied Prince Charles on inspecting the Guard of Honor formed by Grenadier Guards in their traditional bearskin hats.
Members of the King's Troop Royal Horse Artillery performed a gun salute to kick off Trump's visit and the 66th anniversary of Queen Elizabeth's coronation.
The first couple headed inside the palace with the queen to view historical artifacts and artwork in the Royal Collection.
The official state visit comes nearly two years after the president was initially invited. Protesters are expected to welcome the president with much controversy and ceremony, including displaying a 20-foot inflatable blimp of Trump looking like a baby.